Displacement transducer

ABSTRACT

A displacement transducer is comprised of an magnetoresistive element, or an elongated semiconductor member having the magnetoresistive effect. A pair of electrodes are affixed at both ends of this magnetoresistive element, and a third electrode at the center. While an electric current is made to flow therethrough from each of the pair of electrodes to the third electrode, an applied magnetic field is moved thereon toward either side of the third electrode to obtain an output voltage due to the magnetoresistive effect of the element. In another embodiment of the invention, wherein a plurality of metal boundaries are formed at intervals between a pair of electrodes at both ends of an magnetoresistive element, a leading end of an applied magnetic field is inclined to such a degree as to extend between at least two adjoining ones of the metal boundaries.

"United States Patent 1 Kataoka et a1.

[ DISPLACEMENT TRANSDUCER [75] Inventors: Shoel Kataolta, Tanashi-shi,Tokyo; Hideo Yamada, Setagaya-ku, Tokyo, .both of Japan [73] Assignee:Kogyo Gijutsuin (a/k/a Agency of Industrial Science and TechnologyMinistry of International Trade and Industry), Tokyo-To, Japan [22]Filed: Apr. 29, 1971 [21] Appl. No.: 138,508

[30] Foreign Application Priority Data May 1, 1970 Japan 45/37446 [56]References Cited A UNITED STATES PATENTS 11/1966 Jones et a1. 338/32 R X8/1966 Hieronymus... 338/32 H 8/1967 Weiss 338/32 R X [451 Aug. 14, 1973FOREIGN PATENTS OR APPLICATIONS 1,290,341 8/1964 Germany 324/34 PSPrimary Examiner-C. I... Albritton AttorneyRobert E. Burns and Emmanuel.I. Lobato [5 7] ABSTRACT A displacement transducer is comprised of anmagnetoresistive element, or an elongated semiconductor member havingthe magnetoresistive effect. A pair of electrodes are afiixed at bothends of this magnetoresistive element, and a third electrode at thecenter. While an electric current is made to flow therethrough from eachof the pair of electrodes to the third electrode, an applied magneticfield is moved thereon toward either side of the third electrode toobtain an output voltage due to the magnetoresistive effect of theelement. In another embodiment of the invention, wherein a plurality ofmetal boundaries are formed at intervals between a pair of electrodes atboth ends of an magnetoresistive element, a leading end of an appliedmagnetic field is inclined to such a degree as to extend between atleast two adjoining ones of the metal boundaries.

10 Claims, 24 Drawing Figures Patented Aug. 14,1973 3,753,202

8 Sheets-Sheet 4 F|G.7(b)

FIG.7(0) I I2b Patented Aug. 14,1973 3,753,202

8 Sheets-Sheet Patented Aug.1 4,1973 3,753,202

8 Sheets-Sheet 8 bl b2 CHANNELH) CHANNELUI) BACKGROUND OF THE INVENTIONThis invention relates to a displacement transducer wherein displacementof an applied magnetic field from its predetermined position on asemiconductor element is converted into a voltage due to itsmagnetoresistive effect, i.e. the change in its electrical resistancecaused by the applied magnetic field. The semiconductor element with itsmagnetoresistive effect is referred to as the magnetoresistive element"throughout the present specification.

Conventional versions of such displacement-tovoltage transducer include,for example, a slide-type potentiometric device wherein an electrode ismade to slide on a resistance element. The mechanical contact exploitedin this prior device has resulted in ready damage and wear of therelated parts and has also led to the production of too much noise.When, specifically, a wirewound resistor is employed as the resistanceelement, the output voltage has not varied smoothly enough, but ratherstepwise, along with change in the amount of the displacement. Theprovision of the slidetype potentiometer has also made the overallapparatus considerably bulky.

There are some known devices which attempt to promote themagnetoresistive effect of a semiconductor by dividing it into severalportions by means of transverse metal boundaries. Here again, however,the metal boundaries so dividing the magnetoresistive element has causedstepwise change in the output voltage as a magnetic field is moved onthe element perpendicularly to the strips.

According to a displacement transducer already applied for a patent bythe present applicant and now pending (the United States applicationSer. No. 817,934), two individual magnetic fields are required whichmove in an interrelated manner. Moreover, the

permitted ranges of movements of the magnetic fields SUMMARY OF THEINVENTION It is an object of the'present invention to provde adisplacement transducer of simple construction which delivers agreatoutput voltagein comparison with the amount of displacement of amagnetic field by making efficient use of the magnetoresistive effect ofa semiconductor.

Another object of the invention is to provide a displacement transducercapable of converting twodimensional displacement of a magnetic fieldinto two independent electrical quantities.

Another object of the invention is to provide a displacement transducerwherein one or both ends of a magnetic field applied to anmagnetoresistive element having a plurality of metal strips orboundaries are inclined in such a manner that an output voltage isobtained which varies smoothly enough along with change in the amountvof displacement of the magnetic field.

A further object of the invention is to provide a displacementtransducer wherein only one mobile magnetic field is required to producean output voltage equal to that hitherto obtained only by theapplication of two individual magnetic fields, the one magnetic field inthe displacement transducer of the invention being permitted to movethrough a greater angle or for a greater distance.

Other objects, features and advantages of this invention will beapparent from the following detailed description when read in connectionwith the accompanying drawings.

. BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIGS. 1(a), (b) and (c) are both schematic and explanatoryrepresentations of a displacement transducer in accordance with theconcepts of the present invention;

FIG. 2 schematically illustrates a second embodiment of the inventionwherein the transducer is designed to convert two-dimensionaldisplacement of a magnetic field into two independent electricalquantities;

FIG. 3 also schematically illustrates the magnetoresistive element inFIG. 2 in combination with a circuit adapted for application of aconstant current to each the four electrodes;

FIGS. 4(a) and (b) are schematic, fragmentary representations ofmodified examples of the shape of the magnetoresistive element in FIGS.2 and 3;

FIG. 5 schematically illustrates an example of application of thedisplacement transducer of FIGS. 2 and 3 in a pickup of a stereophonicrecord player;

FIG. 6 schematically illustrates a third embodiment of the inventionwherein the transducer is designed to convert rotary displacement of amagnetic field into a voltage;

FIGS. 7(a) and (b) are vertical and horizontal sectional views,respectively taken along the lines XX and XX' indicated in thecorresponding drawings, showing a more practical configuration of thedisplacement transducer of FIG. 6;

FIG. 8(a) is a both schematic and explanatory representation of afurtherembodiment of the invention, while FIGS. 8(b) and 8(c) are showcharacteristics curves in prior art;

FIG. 9 is a graph showing a linear relationship between themagnetoresistance of the electromagneto element in FIG. 8(a) and theamount of the displacement of the magnetic field in the transduceraccording to the invention;

FIG. 10 schematically illustrates a modified example of the shape of theleading end of the magnetic field in FIG. 8(a);

FIG. 11 is both a schematic and explanatory representation of a stillfurther embodiment of the invention,

FIGS. 12 (a) (b) and 12 (c) are both schematic and explanatoryrepresentations of a further embodiment of the invention comprising aplurality of magnetoresistive elements as shown in FIG. 11 to which arecommonly applied a single displaceable magnetic field.

FIG. 13 schematically illustrates still a further embodim'ent of thepresent invention comprising a pair of parallel magnetoresistiveelements to which is commonly applied a single displaceable magneticfield; FIG. 14 also schematically illustrates a modified example of thedisplacement transducer of FIG. 13, comprising a. pair of parallelmagneto resistive elements each in the shape of an arc;

FIG. 15 is both a schematic and explanatory representation of a stillfurther embodiment of the invention comprising a pair ofmagnetoresistive elements to which is commonly applied a single magneticfield;

FIG. 16 also schematically illustrates a modified example of thedisplacement of FIG. 15.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, andfirst of all to FIG.

. 1(a), (b) and (c) in order to describe the first embodiment of theinvention illustrated therein, a magnetoresistive element 1 is affixedwith electrodes 2, 3 and 4 at its both ends and center. Themagnetoresistive element may be made of materials havingmagnetoresistive effect, for example, material of high mobility such asa compound consisted of the elements selected from third and fifth groupof perioderic table, for example, InSb, InAs, GaAs. Constant currents Iare made to flow through this magnetoresistive element 1 from theelectrodes 2 and 3 at both ends to the center electrode 4 or vice versa.If, then, a unidirection magnetic field M is applied at the center ofthis magnetoresistive element 1 in a direction at right anglestherewith, as illustrated in FIG. 1(a), the electrical resistance ofthis element 1 is increased at its part being subjected to the magneticfield M. Since, however, equal portions of the left hand half and theright hand half of the magnetoresistive element 1 are subjected to themagnetic field M, and since the equal remaining portions thereof arenot, electrical resistance R between the electrodes 2 and 4 equalselectrical resistance R between the electrodes 3 and 4. Let thiselectrical resistance R or R be represented by R.

Suppose now that the unidirectional magnetic field M is moved in theright hand direction'bythe amount equal to Ax as illustrated in FIG.1(b). The electrical resistance R between the electrodes 3 and 4 of themagnetoresistive element 1 will be increased to R AR since then theright hand half is subjected to the magnetic field M at its portionincreased correspondingly to the amount of the magnetic field M from itscentral position. On the other hand, the electrical resistance R betweenthe electrodes 2 and 4 of the magnetoresistive element 1 has to bedecreased to R AR as its por-, tion being applied with the magneticfield M is decreased correspondingly.

If equal constant currents I are made to flow through thismagnetoresistive element 1 from the electrodes 2 and 3, respectively, tothe center electrode 4, voltage V between the electrodes 3 and 4 variesfrom IR to IR I-AR, while voltage V between the electrodes 2 and 4varies from IR to IR I'AR. Since the overall voltage between theelectrodes 2 and 3 thus totals 2AR-I, there is obtained an outputvoltage in proportion to the displacement Ax of the magnetic field Mfrom output terminals a and b attached to the electrodes 2 and 3,respectively. It will be needless to say that when the magnetic field Mmakes a negative displacement, i.e. in the left hand direction asillustrated in FIG. 1(0), a negative output voltage is obtained whichalso is proportional to the amount of the displacement.

The fundamental concepts underlying the above described first embodimentof the invention are also exploited in the second embodiment illustratedin FIG. 2, in which two-dimensional displacement of a magnetic field isconverted into two independent voltages. Two magnetoresistive la and lbare combined into the shape of a cross. Four electrodes 2, 3, 6 and 7are affixed at the ends of the four arms, and another electrode 5 at thecenter. Square magnetic field M is applied centrally to this crossshaped magnetoresistive element as illustrated in the drawing, andconstant currents I are made to flow therethrough from the fourelectrodes 2, 3, 6 and 7 to the common center electrode 5 or vice versa.In this instance, if the four arms are of the same material and of thesame shape, and if the square magnetic field M is located exactlycentrally of this cross shaped magnetoresistive element, the arms willhave the same electrical resistance so that no voltage will be existentbetween the electrodes 2 and 3 or between the electrodes 6 and 7.

If the magnetic field M is moved horizontally on this cross shapedmagnetoresistive element as viewed in FIG. 2, a voltage corresponding tothe amount of the horizontal displacement from the exactly centrallocation is obtained terminals 0 and b attached to the electrodes 2 and3 of the horizontally extending arms, for reasons described already inconnection with the first embodiment of the invention illustrated inFIG. 1. Since, however, the magnetic field is assumed to be exactlysquare in shape, its only horizontal displacement does not cause anychange in the areas of those portions of the vertically extending armswhich are subjected thereto. No voltage is then produced betweenterminals 0 and d attached to the electrodes 6 and 7. For the samereasons, vertical displacement of the magnetic field M produces acorresponding voltage between the terminals c and d and no voltagebetween the terminals a and b. Considered generally, when the magneticfield M is moved in a certain direction, there is obtained between theterminals a and b and/or between the terminals c and d a voltage orvoltages depending upon of the horizontal and vertical components ofdisplacement of the magnetic field M from its exactly central locationof the magnetoresistive element.

In practice, however, the shapes and the materials, and therefore theelectrical resistance, of the respective arms of the linear and thecross shaped magnetoresistive element (illustrated in FIGS. 1 and 2) maynot be alike. The constant currents I that are made to flow through therespective arms may not necessarily be equal, either. In such cases alocation of the magnetic field M- at which no voltage is producedbetween the associated pair or pairs of the terminals .can be regardedas an origin of its oneor two-dimensional displacement. Displacement ofthe magnetic field M from its origin thus determined will be convertedinto desired electrical voltage. I I I With reference now to FIG. 3,resistances 8 of appropriately high value are respectively connected inseries with the electrodes 2, 3, 6 and 7 at the ends of four arms of thecross shaped magnetoresistive element of FIG. 2, the other ends of theresistances 8 being all interconnected. A power supply 9 capable ofdelivering a constant voltage is connected between the interconnectedends of the resistances 8 and the center electrode 5. The desiredfunctions of the cross shaped magnetoresistive element describedprecedingly with relation to FIG. 2 can beobtained by this examplaryconfiguration. It will be understood that the semiconductor making upthe cross shaped magnetoresistive element may not be all of one piece,but that only the necessary portions of its arms may be made of separatesemiconductor members only if these are properly electricallyinterconnected at the center.

upon applications. For example, they may be in the zigzag shape asillustrated in FIGS. 4(a) and (b). The increased overall length of eacharm serves to increase the resistance. It will also be obvious that themagnetoresistive effect of the semiconductor in general is furtherpromoted when a number of metal boundaries are built therein.

FIG. 5 illustrates an example of application of the above describedtwo-dimensional displacement transducer in a pickup of a stereophonicrecord player. A stylus 11 is coupled to a square shaped member ofmagnetic material adapted for production of a mobile magnetic field, andits right angled displacements caused by a two-channel groove of astereo record are respectively translated into electrical signals.

FIG. 6 illustrates a third embodiment of the invention, in which thefundamental principles described above with reference to FIG. 1 areutilized for conversion of rotary displacement of a magnetic field intoa corresponding voltage. A magnetoresistive element 1 is in a circularconfigulation with a gap, with electrodes 2, 3 and 4 affixed at bothends and at a center. Suppose that an arched magnetic field M is firstapplied concentrically with the said magnetoresistive element 1 and soas to be in symmetry on both sides of the center electrode4, and thatelectric currents I of equal magnitude are made to flow from theelectrodes 2 and 3 at both ends to the center electrode 4. No voltagewill then be produced as already described. But when the magnetic fieldM is turned through an angle A0, a voltage corresponding thereto will bedelivered from the terminals connected to the electrodes 2 and 3.

FIG. 7(a) and (b) show a more practical example of such rotarydisplacement transducer. The magnetoresistive element 1 of asemiconductor material is mounted, through an insulator 13, centrallyupon a magnetic member 12a in the shape of an upwardly rimmed disk asillustrated in FIG. 7(a). On the other hand, with reference to FIG.7(b), there is provided a corresponding magnetic member 12b in the shapeof a downwardly rimmed disk to which is secured a permanent magnet 14 ofsuitable cross sectional shape, for example, semicircular or sectorshape. A center of circle formed by arc'of permanent magnet 14 coincideswith a center of the magnetoresistive element. This magnetic member 12bwith its permanent magnet 14 is concentrically mounted on the formermagnetic member 12a through a guide 15, the vertical length of thepermanent magnet 14 being such that when the magnetic members 12a and12b are so combined, there will be a slight spacing between itself andthe magnetoresistive element 1. In this manner the location ofthemagnetic field produced by the permanent magnet 14 on themagnetoresistive element 1 can be varied relative to the latter byturning the magnetic member 12b. As an added advantage the desiredmagnetic field in the above configuration is not susceptible todemagnetization and can substantially permanently retain its initialintensity.

- In'FIG. 8(a) a number of metal boundaries 16 are formed atsubstantially constant intervals between electrodes 2 and 3 of anmagnetoresistive element 10 with a view to further improvement of itsmagnetoresistive characteristics. These metal boundaries 16 are formedeither by vacuum evaporation, plating or any other.

suitable process. Since then the electric field at each of these metalboundaries 16 has to be perpendicular to the boundaries between themetal and the semiconductor, the direction of current flow is inclinedby the socalled Hall angle when a magnetic field is applied. The resultis more pronounced magnetoresistive effect.

When, however, a magnetic field M with a fiat or noninclined end A(indicated by a two dotted line in the drawing) in prior art is moved onthe above configured magnetoresistive element 1c, the resultant changein its electrical resistance does not always exhibit a linearrelationship with the amount of displacement of the magnetic field, asgraphically demonstrated in FIGS. 8(b) and 8(c). This obviously is dueto the fact that increase in the electrical resistance of themagnetoresistive element 10 caused upon application of a magnetic fieldthereto is most marked at the boundaries between the metal boundariesand the semiconductor.

According to the present invention, in order to eliminate such anon-smooth relationship between the change in the electrical resistanceand the amount of the displacement, there is applied to themagnetoresistive element 10 a magnetic field having an inclined end P asindicated by a dotted line in FIG. 8(a). It is imperative that the end Pof the magnetic field M is inclined to such a degree as to extendbetween at least two adjoining ones of the metal boundaries 16 wherebyeach of the successive boundaries 16 may gradually go in and out of themagnetic field M as the same is displaced thereon.

FIG. 9 is a graphic representation of the relationship between thechange in the electrical resistance of the magnetoresistance element 10and the amount of the displacement of the magnetic field M having theinclined end P. It will be obvious that the end of the magnetic field Mcan be sharpended as indicated by a dashed line of FIG. 10 to obtain thesame results.

Direction of the inclination may be in any direction along the widthand/or the thickness of said element.

FIG. 1 1 shows an example of application of the foregoing embodiment ofthe present invention in a threeterminal potentiometer utilizing amagnetoresistive element. FIG. 11(a) schematically illustrates athreeterminal potentiometric transducer comprising a magnetoresistiveelement 1, a pairof electrodes 2 and 3 at both ends, a center electrode4 and a number of metal boundaries 16. According to the prior art, amagnetic field B having flat or noninclined ends A, as indicated bydashed lines in the drawing, has been applied only to approximately onehalf of the entire length of the magnetoresistive element 1. By movingthe former relative to the latter, a desired variable fraction V ofinput voltage V which has been applied between terminals 11 and battached to the electrodes 2 and 4, respectively, is obtained betweenterminals b and c attached to the electrodes 4 and 3 or betweenterminals a and c attached to the electrodes 2 and 4, respectively. Uponcloser observation of this voltage V between the voltage dividingelectrodes 4 and 3, for instance, it has been revealed that the voltagefraction V does not change smoothly enough along with variation of theamount of displacement of the magnetic field B, but changes non-smoothlyin similar to those illustrated in FIGS. 8(b) and 8(c). Contrastively, asmooth relationship therebetween as shown in FIG. 9 is obtainable by thedisplacement of an applied magnetic field M in accordance with thepresent invention. The both ends of this magnetic field M are inclinedenough to extend between at least two adjoining ones of the metalboundaries 16.

FIG. 12(a) and (b) illustrate two other examples of the combination ofFIG. 11(a). In each of the illustrated configurations a plurality ofmagnetoresistive element 1 are arranged in parallel to which is commonlyapplied a magnetic field M, with a view to more pronounced change in theoutput voltage V as the magnetic field M is moved on themagnetoresistive elements 1 from one end to the other. Moreover, sinceboth ends of the magnetic field M are inclined as described already inconnection with FIG. 11(a), smooth variation of the output voltage isensured as illustrated in FIG. 12(0).

FIG. 13 illustrates a further embodiment of the present invention,wherein a pair of magnetoresistive elements 1 and 1 are arranged inparallel with each other and are connected in parallel by means of aconductor 18 extending between electrodes 2 and 2' and a conductor 19extending between electrodes 3 and 3'. A power supply capable of feedingelectrical energy in the form of a constant voltage V is connectedbetween the electrodes 2' and 3. Output terminals a and b are connectedto output electrodes 4 and 4' which are provided in the center of themagnetoresistive elements 1 and 1.

In operation the voltage V is applied between the electrodes 2' and 3,and a unidirectional'magnetic field M is applied which extends over notmore than approximately one half of the length of each of the magnetoresistive elements 1 and 1. By moving the magnetic field M relative to themagnetoresistive elements 1 and 1' there will be obtained between theoutput terminals a and b a combined output voltage of themagnetoresistive elements 1 and 1' depending upon the amount of thedisplacement. Hence only one magnetic field need be applied to producean output voltage obtained heretofore by the application of two separatemagnetic fields as described in said co-pending application Ser. No.817934.

A modified example of the embodiment of FIG. 13 is illustrated in FIG.14, in which a pair of magnetoresistive elements 1 and l'- are made inthe shape of an are or arcuate sector approximating a complete circleand are arranged concentrically. An arcuate unidirectional magneticfield M is applied thereto in a manner described precedingly inconnection with the third embodiment of the invention illustrated inFIG. 6.

Other details of configuration are patterned after the foregoingembodiment of FIG. 13. In this manner a voltage of :ZAV is producedbetween output terminals a and b by the displacement of the magneticfield M through an angle of :AO. The voltage AV is proportional to theangle A0.

Although there have been described embodiments obtaining only one outputin correspondence to the displacement of the magnetic field, it will beapparent that there can be'obtained two outputs of opposite polaritiesin other embodiments, if two magnetoresistive element are provided undera common magnetic field, and voltages are applied to these elements.

For instance, in an embodiment shown in FIG. 15, magnetoresistiveelements 1 and l' affixed with electrodes 2a, 3a, 4a and 2b, 3b, 412,respectively, are arranged in parallel, and a magnetic field is commonlyapplied to both of the magnetoresistive elements 1a and lb, so thatchannel I and channel I] are thereby formed.

When an input voltage is applied across terminals a1 and b1 connected tothe electrodes 2a and 3a of the channel I, an output voltage is to beobtained between the terminals cl and bl. However, minimum voltage willappear across the output terminals when the magnetic field M is appliedonly to the upper half of the magnetoresistive element 1, and an outputvoltage will be increased when the magnetic field is moved downward andthe maximum output voltage is obtained when the magnetic field isapplied only to the lower half of the magnetoresistive element.

Contrastively, in the channel II, an output voltage is obtained fromterminals a2 and 02 when an input voltage is applied between theterminals a2 and 122. Hence, in this case a maximum output voltage isproduced when the magnetic field M is applied only to the upper half ofthe magnetoresistive element 1, the output voltage gradually decreasesas the magnetic field is moved part the center electrode 4b to the lowerhalf.

Thus in the embodiment shown in FIG. 15, the characteristic of theoutput voltage in two channels against the displacement of the magneticfield M are opposite to each other and thus the adjustment in balancebetween the output voltages from the channel I and channel II can easilybe achieved by the movement of the single magnetic field.

In FIG. 16, there is indicated a modified example of the foregoingembodiment of FIG. 15 wherein the mag netic field is moved rotationally.As illustrated, magnetoresistive elements 1 and 1' are arrangedconcentrically, and a semicircular magnetic field M is applied commonlyto both of the elements. The operation of this example is quite similarto that described in connection with the embodiment of FIG. 15. Theseembodiments illustrated in FIGS. 15 and 16 are very use ful for thebalance control in a stereophonic instrument.

' Throughout all the foregoing embodiments of the present invention, aswell as the examples of their modification or application, the magneticfield M may be produced either by a permanent magnet, a coil or anyother means suitable for the objects of the invention. Further, althoughthe invention has shown and described in the foregoing in very specificaspects thereof, it will be obvious to those skilled in the art thatfurther modifications or applications of the invention may be resortedto in a manner limited only by a just interpretation of the appendedclaims.

The input voltage and current may be variable. This displacementtransducer may be used as a volume control device of contactless type.

We claim:

1. A transducer for converting the relative displacement of aunidirectional magnetic field into an electrical signal comprising: twogeometrically alike magnetoresistive portions; means for applyingelectrical energy to said magnetoresistive portions to effect currentflow in opposite directions through both portions; means for applying aunidirectional magnetic field simultaneously to both saidmagnetresistive portions to vary the resistance thereof and coactingwith said magnetoresistive portions to allow relative displacementbetween the unidirectional magnetic field and said magnetoresistiveportions; and means connected to said magnetoresistive portions andresponsive to the displacement of the unidirectional magnetic fieldrelative thereto for developing an electrical signal having one polaritywhen the unidirectional magnetic field is displaced in one directionrelative to said magnetoresistive portions from a given reference planeand having an opposite polarity when the unidirectional magnetic fieldis displaced in an opposite directionrelative to said magnetoresistiveportions from said reference plane and having a magnitude proportionalto the extent of displacement from said reference plane.

2. A transducer according to claim 1; wherein said two magnetoresistiveportions comprise two portions of a single magnetoresistive element eachdisposed on opposite sides of said reference plane which extends throughthe geometrical center of said magnetoresistive element.

3. A transducer according to claim 2; wherein said means for applyingelectrical energy and said means for developing an electrical signalinclude a pair of end electrodes each attached to one end of saidmagnetoresistive element, and a center electrode attached to saidmagnetoresistive element at its geometrical center.

4. A transducer according to claim 2, wherein said two magnetoresistiveportions comprise two distinct magnetoresistive elements disposed inparallel relationship and having said reference plane extending throughthe geometrical centers of both said magnetroresistive elements.

5. A transducer according to claim 4; wherein said means for applyingelectrical energy and said means for developing an electrical signalinclude four end electrodes attached respectively to the four ends ofsaid two magnetoresistive elements, and two center electrodes attachedrespectively to the geometrical centers of said two magnetoresistiveelements.

6. A transducer according to claim 4; wherein said two magnetoresistiveelements extend linearly in the directions of relative displacementbetween same and said unidirectional magnetic field.

7. A transducer according to claim 4; wherein said two magnetoresistiveelements extend curvilinearly along a circular arc in the direction ofrelative displacement between same and said unidirectional magneticfield.

8. A transducer according to claim 4; wherein said means for applyingelectrical energy comprises four end electrodes attached respectively tothe four ends of said two magnetoresistive elements, conductorsconnected to said end electrodes electrically connecting said twomagnetoresistive elements in parallel, and means for applying a voltageacross said four electrodes; and wherein said means for developing anoutput signal comprises a pair of center electrodes attachedrespectively to the geometrical centers of said two magnetoresistiveelements developing thereacross said output signal during use of thetransducer.

9. A transducer according to claim 8; wherein said two magnetoresistiveelements extend linearly in the directions of relative displacementbetween same and said unidirectional magnetic field.

10. A transducer according to claim 8; wherein said two magnetoresistiveelements extend curvilinearly along a circular arc in the direction ofrelative displacement between same and said unidirectional magneticfield.

1. A transducer for converting the relative displacement of aunidirectional magnetic field into an electrical signal comprising: twogeometrically alike magnetoresistive portions; means for applyingelectrical energy to said magnetoresistive portions to effect currentflow in opposite directions through both portions; means for applying aunidirectional magnetic field simultaneously to both saidmagnetresistive portions to vary the resistance thereof and coactingwith said magnetoresistive portions to allow relative displacementbetween the unidirectional magnetic field and said magnetoresistiveportions; and means connected to said magnetoresistive portions andresponsive to the displacement of the unidirectional magnetic fieldrelative thereto for developing an electrical signal having one polaritywhen the unidirectional magnetic field is displaced in one directionrelative to said magnetoresistive portions from a given reference planeand having an opposite polarity when the unidirectional magnetic fieldis displaced in an opposite directionrelative to said magnetoresistiveportions from said reference plane and having a magnitude proportionalto the extent of displacement from said reference plane.
 2. A transduceraccording to claim 1; wherein said two magnetoresistive portionscomprise two portions of a single magnetoresistive element each disposedon opposite sides of said reference plane which extends through thegeometrical center of said magnetoresistive element.
 3. A transduceraccording to claim 2; wherein said means for applying electrical energyand said means for developing an electrical signal include a pair of endelectrodes each attached to one end of said magnetoresistive element,and a center electrode attached to said magnetoresistive element at itsgeometrical center.
 4. A transducer according to claim 2, wherein saidtwo magnetoresistive portions comprise two distinct magnetoresistiveelements disposed in parallel relationship and having said referenceplane extending through the geometrical centers of both saidmagnetroresistive elements.
 5. A transducer according to claim 4;wherein said means for applying electrical energy and said means fordeveloping an electrical signal include four end electrodes attachedrespectively to the four ends of said two magnetoresistive elements, andtwo center electrodes attached respectively to the geometrical centersof said two magnetoresistive elements.
 6. A transducer according toclaim 4; wherein said two magnetoresistive elements extend linearly inthe directions of relative displacement between same and saidunidirectional magnetic field.
 7. A transducer according to claim 4;wherein said two magnetoresistive elements extend curvilinearly along acircular arc in the direction of relative displacement between same andsaid unidirectional magnetic field.
 8. A transducer according to claim4; wherein said means for applying electrical energy comprises four endelectrodes attached respectively to the four ends of said twomagnetoresistive elements, conductors connected to said end electrodeselectriCally connecting said two magnetoresistive elements in parallel,and means for applying a voltage across said four electrodes; andwherein said means for developing an output signal comprises a pair ofcenter electrodes attached respectively to the geometrical centers ofsaid two magnetoresistive elements developing thereacross said outputsignal during use of the transducer.
 9. A transducer according to claim8; wherein said two magnetoresistive elements extend linearly in thedirections of relative displacement between same and said unidirectionalmagnetic field.
 10. A transducer according to claim 8; wherein said twomagnetoresistive elements extend curvilinearly along a circular arc inthe direction of relative displacement between same and saidunidirectional magnetic field.